1. Field of the Invention
The present invention relates to a thin film magnetic head having a structure in which a coil is toroidally wound around a magnetic layer, and particularly to a thin film magnetic head capable of improving the magnetization efficiency and properly securing insulation between the coil and the magnetic layer.
2. Description of the Related Art
Any one of Japanese Unexamined Patent Application Publication Nos. 11-273028, 2000-311311 and 20002-170205 and U.S. Pat. No. 6,335,846 B1 discloses a structure in which a coil layer is toroidally wound around a core constituting an inductive head (recording head).
In order to effectively use a three-dimensional space around a core layer, the coil layer is preferably formed in a toroidal shape. It is expected from this that the miniaturization of an inductive head can be realized, and the magnetization efficiency can be improved.
Any of the above-described documents discloses that a lower coil layer formed below a core layer (for example, an upper magnetic layer) is electrically connected, through a connecting portion, to an upper coil layer formed above the core layer.
For example, in Japanese Unexamined Patent Application Publication Nos. 2002-311311 and 2002-170205, as shown in FIG. 16, an insulating layer 1 covers a lower coil layer 3, an insulating layer 2 is formed on a core layer 4 to extend to both sides of the core layer 4 in the track width direction, and through holes 6 are formed in both insulating layers 1 and 2 by an etching technique such as ion milling or the like. Also, connecting portions 7 are formed in the through holes 6 to connect the tops of the connecting portions 7 exposed from the through holes 6 to the bottom of an upper coil layer 5. Although these documents do not show a front view showing the lower coil layer 3, the upper coil layer 5, and the connecting portions 7 as viewed from a surface facing a recording medium, a simple front view is possibly as shown in FIG. 16 in consideration of the contents described in the documents.
However, as shown in FIG. 16, steps 8 are formed between the top of the core layer 4 and the top of the insulating layer 1, and thus the insulating layer 2 formed on the core layer 4 to extend to both sides thereof does not adhere to both side surfaces 4a of the core layer 4 in the track width direction, or a pin hole easily occurs in the insulating layer 2 deposited on both side surfaces 4a because the insulating layer 2 is very thin. Therefore, insulation cannot be sufficiently maintained between the upper coil layer 5 formed on the insulating layer 2 and both side surfaces 4a of the core layer 4 to easily cause a short circuit between the upper coil layer 5 and the core layer 4, thereby deteriorating recording characteristics.
In order to solve this problem, the deposition time of the insulating layer 2 may be simply increased to increase the thickness of the insulating layer 2 deposited on both side surfaces 4a of the core layer 4. In this case, the insulating layer 2 deposited on the top of the core layer 4 becomes excessively thick to increase the distance between the core layer 4 and the upper coil layer 5, thereby deteriorating the magnetization efficiency.